1. Field of the Invention
The present invention relates to an image forming apparatus and, more specifically, to an image forming apparatus that can data-access to a non-contact type data storage circuit mounted on a detachable unit in the image forming apparatus.
2. Description of the Related Art
In 4-cycle type color printers including one photoreceptor drum and four developing units for forming a toner image on the photoreceptor drum, it is currently a dominant trend to provide a non-contact type IC memory on the developing unit. The non-contact type IC memory stores information related to the developing unit (in the following, also referred to as developing unit information). The developing unit information includes an ID code, serial number, date of manufacturing, lot number, cartridge identifying information, color information, toner consumption and so on.
Generally, in a 4-cycle type color printer, in a step in which a latent electro-static image is formed on the surface of photoreceptor drum and toner is attracted to the latent electrostatic image, a high-voltage AC signal is generated internally. If a data access to the non-contact type IC memory (hereinafter also referred to as a wireless communication process) takes place in the period in which the high-voltage AC signal is generated internally (hereinafter also referred to as a high-voltage generating period), it is likely that the high-voltage AC signal hinders normal data-access to the non-contact type IC memory.
In view of the foregoing, Japanese Laid-Open Patent Publication No. 11-316534 discloses a technique that reduces the influence of high-voltage AC signal mentioned above, by preventing the radio frequency used at the time of wireless communication process from becoming a multiple of the frequency of high-voltage AC signal.
According to the technique disclosed in Japanese Laid-Open Patent Publication No. 11-316534, however, the radio frequency of the signal used for the wireless communication process possibly becomes a multiple of the frequency of high-voltage AC signal because of circuit characteristic variations and temperature conditions, and therefore, possible influence of the high-voltage AC signal remains.
In the 4-cycle type color printer, the four developing units are provided on one developing rack, which rack rotates. Therefore, the non-contact type IC memory attached to the developing unit also rotates. Therefore when a large amount of data is to be transmitted/received to and from the non-contact type IC memory that rotates, the wireless communication process could fail unless the time for wireless communication is made longer correspondingly.